Persistent but reversible coronary microvascular dysfunction after bypass grafting

Comparison of Fractional Flow Reserve and Myocardial Perfusion Imaging in Saphenous Vein Grafts

BACKGROUND

Revascularization decision-making for saphenous vein grafts (SVGs) relies on angiographic lesion severity estimation, as studies on fractional flow reserve (FFR) for detecting ischemia in SVGs are scarce.

AIMS

To compare FFR and quantitative coronary angiography (QCA) of SVGs against myocardial perfusion imaging (MPI) and to establish an optimal FFR threshold for SVGs.

METHODS

This cross-sectional registry study included symptomatic patients with prior coronary artery bypass grafting who underwent single-photon emission computed tomography, positron emission tomography, or stress perfusion cardiac magnetic resonance imaging and had FFR measurements of ≥ 1 SVGs. We matched the myocardial territory supplied by the SVGs to ischemia on MPI. The optimal FFR threshold for SVGs was determined using the Youden index. Diagnostic performance measures were calculated and compared for FFR (0.80 and the optimal threshold) and for QCA (diameter stenosis ≥ 50%).

RESULTS

This study included 80 patients (mean age 73 ± 7 years, 68 [85%] male) with 94 SVGs, of which 38 (40%) supplied ischemic myocardium. Areas under the curve between FFR and QCA were comparable (0.73 vs. 0.65, p = 0.181). The optimal cutoff value of FFR was 0.94. FFR ≤ 0.94 showed higher sensitivity (63%) and negative predictive value (75%) compared to FFR ≤ 0.80 (32% [p < 0.001] and 64% [p = 0.007]) and QCA (37% [p = 0.002] and 65% [p = 0.021]), but with lower specificity (75%) than FFR ≤ 0.80 (84%, p = 0.021). Positive predictive value and overall accuracy were similar across all methods.

CONCLUSIONS

FFR and QCA had comparable moderate diagnostic performance for detecting SVG failure determined by MPI. The optimal FFR cutoff in SVGs is higher than 0.80, resulting in higher sensitivity and negative predictive value compared to FFR ≤ 0.80 and QCA, at the expense of reduced specificity.

Myocardial perfusion imaging in advanced coronary artery disease

Myocardial perfusion imaging (MPI) is widely adapted as a noninvasive technique to assess the presence and extent of ischemia in patients with symptoms suggestive of obstructive coronary artery disease (CAD). However, as CAD advances, several factors can complicate the interpretation of MPI, subsequently impacting clinical decision-making. This review focuses on the utility of MPI by means of cardiac magnetic resonance (CMR) imaging, single-photon emission computed tomography (SPECT) and positron emission tomography (PET) in patients with advanced CAD-the latter characterized by documented CAD (i.e. prior myocardial infarction [MI] and/or percutaneous coronary intervention [PCI]), prior coronary artery bypass grafting (CABG) or the presence of a chronic total occlusion (CTO). It will discuss factors impacting the interpretation of MPI, the diagnostic performance for detecting obstructive CAD and coronary microvascular dysfunction (CMD), as well as the role of MPI in guiding revascularization.

Quantitative analysis of myocardial blood flow in surgically revascularized and not revascularized myocardial segments. A pilot PET study

PURPOSE

To prospectively compare changes in myocardial blood flow (MBF) and myocardial flow reserve (MFR) in multivessel coronary artery disease (MVCAD) patients undergoing incomplete revascularization (IR) versus complete revascularization (CR) by coronary artery bypass grafting (CABG).

METHODS

Seven male patients (age 68 ± 9 years) with MVCAD underwent myocardial perfusion PET/CT with [13N]ammonia before and at least 4 months after CABG. Segmental resting and stress MBF as well as MFR were measured. Resting and during stress left ventricle ejection fraction (LVEF) were also calculated.

RESULTS

Three patients (43%) underwent CR and four (57%) IR. Among 119 myocardial segments, 101 (85%) were revascularized, and 18 (15%) were not. After CABG, stress MBF (mL/min/gr) and MFR are significantly increased in all myocardial segments, with a greater increase in the revascularized segments (p = 0.013). In both groups, LVEF significantly decreased during stress at baseline PET (p = 0.04), but not after CABG.

CONCLUSION

Stress MBF and MFR significantly improve after CABG in both revascularized and not directly revascularized myocardial segments. IR strategy may be considered in patients with high surgical risk for CR.

Chinese expert consensus on the diagnosis and treatment of coronary microvascular diseases (2023 Edition)

Since the four working groups of the Chinese Society of Cardiology issued first expert consensus on coronary microvascular diseases (CMVD) in 2017, international consensus documents on CMVD have increased rapidly. Although some of these documents made preliminary recommendations for the diagnosis and treatment of CMVD, they did not provide classification of recommendations and levels of evidence. In order to summarize recent progress in the field of CMVD, standardize the methods and procedures of diagnosis and treatment, and identify the scientific questions for future research, the four working groups of the Chinese Society of Cardiology updated the 2017 version of the Chinese expert consensus on CMVD and adopted a series of measures to ensure the quality of this document. The current consensus has raised a new classification of CMVD, summarized new epidemiological findings for different types of CMVD, analyzed key pathological and molecular mechanisms, evaluated classical and novel diagnostic technologies, recommended diagnostic pathways and criteria, and therapeutic strategies and medications, for patients with CMVD. In view of the current progress and knowledge gaps of CMVD, future directions were proposed. It is hoped that this expert consensus will further expedite the research progress of CMVD in both basic and clinical scenarios.

Impact of cardiac history and myocardial scar on increase of myocardial perfusion after revascularization

PURPOSE

We sought to assess the impact of coronary revascularization on myocardial perfusion and fractional flow reserve (FFR) in patients without a cardiac history, with prior myocardial infarction (MI) or non-MI percutaneous coronary intervention (PCI). Furthermore, we studied the impact of scar tissue.

METHODS

Symptomatic patients underwent [15O]H2O positron emission tomography (PET) and FFR before and after revascularization. Patients with prior CAD, defined as prior MI or PCI, underwent scar quantification by magnetic resonance imaging late gadolinium enhancement.

RESULTS

Among 137 patients (87% male, age 62.2 ± 9.5 years) 84 (61%) had a prior MI or PCI. The increase in FFR and hyperemic myocardial blood flow (hMBF) was less in patients with prior MI or non-MI PCI compared to those without a cardiac history (FFR: 0.23 ± 0.14 vs. 0.20 ± 0.12 vs. 0.31 ± 0.18, p = 0.02; hMBF: 0.54 ± 0.75 vs. 0.62 ± 0.97 vs. 0.91 ± 0.96 ml/min/g, p = 0.04). Post-revascularization FFR and hMBF were similar across patients without a cardiac history or with prior MI or non-MI PCI. An increase in FFR was strongly associated to hMBF increase in patients without a cardiac history or with prior MI/non-MI PCI (r = 0.60 and r = 0.60, p < 0.01 for both). Similar results were found for coronary flow reserve. In patients with prior MI scar was negatively correlated to hMBF increase and independently predictive of an attenuated CFR increase.

CONCLUSIONS

Post revascularization FFR and perfusion were similar among patients without a cardiac history, with prior MI or non-MI PCI. In patients with prior MI scar burden was associated to an attenuated perfusion increase.

Coronary artery bypass grafting transiently improves myocardial flow reserve in patients with impaired left ventricular function

BACKGROUND

Myocardial flow reserve (MFR) derived from 13N-ammonia positron emission tomography is an index used to evaluate ischemic cardiomyopathy and predict the prognosis of patients with coronary artery disease (CAD). This study aimed to evaluate the short-term changes in MFR in patients who underwent coronary artery bypass grafting (CABG). In addition, as a reference, we showed the changes in MFR in the percutaneous coronary intervention (PCI) and optimal medical therapy (OMT) patient groups.

METHODS

To determine the short-term effects of CABG in CAD with left ventricular dysfunction, myocardial blood flow (MBF) and MFR were measured before and after CABG. Additionally, we showed changes in MBF and MFR of the PCI and OMT patient groups during treatment.

RESULTS

We observed that resting MBF did not significantly increase from baseline to post-CABG (0.84 ± 0.32 vs. 0.83 ± 0.23, P = 0.958); however, stress MBF increased significantly from baseline to post-CABG (1.23 ± 0.64 vs. 1.49 ± 0.42, P < 0.001). The global MFR increased significantly from baseline to post-CABG (1.49 ± 0.42 mL/g/min vs. 1.91 ± 0.51 mL/g/min, P < 0.001). Additionally, stress and resting ejection fraction (EF) significantly increased (stress EF: 42 ± 18.7% vs. 50.9 ± 18%, P = 0.005; resting EF: 45.8 ± 19.5% vs. 52.1 ± 19.4%, P = 0.031).

CONCLUSIONS

This study demonstrated that CABG significantly improved MFR in a short period of time with left ventricular dysfunction. These findings suggest that epicardial coronary artery patency restores myocardial microcirculatory dysfunction in the short term.

Non-invasive Ischaemia Testing in Patients With Prior Coronary Artery Bypass Graft Surgery: Technical Challenges, Limitations, and Future Directions

Coronary artery bypass graft (CABG) surgery effectively relieves symptoms and improves outcomes. However, patients undergoing CABG surgery typically have advanced coronary atherosclerotic disease and remain at high risk for symptom recurrence and adverse events. Functional non-invasive testing for ischaemia is commonly used as a gatekeeper for invasive coronary and graft angiography, and for guiding subsequent revascularisation decisions. However, performing and interpreting non-invasive ischaemia testing in patients post CABG is challenging, irrespective of the imaging modality used. Multiple factors including advanced multi-vessel native vessel disease, variability in coronary hemodynamics post-surgery, differences in graft lengths and vasomotor properties, and complex myocardial scar morphology are only some of the pathophysiological mechanisms that complicate ischaemia evaluation in this patient population. Systematic assessment of the impact of these challenges in relation to each imaging modality may help optimize diagnostic test selection by incorporating clinical information and individual patient characteristics. At the same time, recent technological advances in cardiac imaging including improvements in image quality, wider availability of quantitative techniques for measuring myocardial blood flow and the introduction of artificial intelligence-based approaches for image analysis offer the opportunity to re-evaluate the value of ischaemia testing, providing new insights into the pathophysiological processes that determine outcomes in this patient population.

Improved regional myocardial blood flow and flow reserve after coronary revascularization as assessed by serial 15O-water positron emission tomography/computed tomography

AIMS

Myocardial perfusion imaging without and with quantitative myocardial blood flow (MBF) and myocardial flow reserve (MFR) plays an important role in the diagnosis and risk stratification of patients with stable coronary artery disease (CAD). We aimed to quantify the effects of coronary revascularization on regional stress MBF and MFR and to determine whether the presence of subendocardial infarction was associated with these changes.

METHODS AND RESULTS

Forty-seven patients with stable CAD were prospectively enrolled. They underwent 15O-water positron emission tomography at baseline and 6 months after optimal medical therapy alone (n = 16), percutaneous coronary intervention (PCI) (n = 18), or coronary artery bypass grafting (CABG) (n = 13). Stenosis of ≥50% diameter was detected in 98/141 vessels (70%). The regional MFR was significantly increased from baseline to follow-up [1.84 (interquartile range, IQR 1.28-2.17) vs. 2.12 (IQR 1.69-2.63), P < 0.001] in vessel territories following PCI or CABG due to an increase in the stress MBF [1.33 (IQR 0.97-1.67) mL/g/min vs. 1.64 (IQR 1.38-2.17) mL/g/min, P < 0.001], whereas there was no significant change in the regional stress MBF or MFR in vessel territories without revascularization. A multilevel mixed-effects models adjusted for baseline characteristics, subendocardial infarction assessed by cardiovascular magnetic resonance imaging, and intra-patient correlation showed that the degree of angiographic improvement after coronary revascularization was significantly associated with increased regional stress MBF and MFR (P < 0.05 for all).

CONCLUSION

Coronary revascularization improved the regional stress MBF and MFR in patients with stable CAD. The magnitude of these changes was associated with the extent of revascularization independent of subendocardial infarction.

EANM procedural guidelines for PET/CT quantitative myocardial perfusion imaging

The use of cardiac PET, and in particular of quantitative myocardial perfusion PET, has been growing during the last years, because scanners are becoming widely available and because several studies have convincingly demonstrated the advantages of this imaging approach. Therefore, there is a need of determining the procedural modalities for performing high-quality studies and obtaining from this demanding technique the most in terms of both measurement reliability and clinical data. Although the field is rapidly evolving, with progresses in hardware and software, and the near perspective of new tracers, the EANM Cardiovascular Committee found it reasonable and useful to expose in an updated text the state of the art of quantitative myocardial perfusion PET, in order to establish an effective use of this modality and to help implementing it on a wider basis. Together with the many steps necessary for the correct execution of quantitative measurements, the importance of a multiparametric approach and of a comprehensive and clinically useful report have been stressed.

Impact of Revascularization on Absolute Myocardial Blood Flow as Assessed by Serial [ 15 O]H 2 O Positron Emission Tomography Imaging

Background:

The main goal of coronary revascularization is to restore myocardial perfusion in case of ischemia, causing coronary artery disease. Yet, little is known on the effect of revascularization on absolute myocardial blood flow (MBF). Therefore, the present prospective study assesses the impact of coronary revascularization on absolute MBF as measured by [ 15 O]H 2 O positron emission tomography and fractional flow reserve (FFR) in patients with stable coronary artery disease.

Methods and Results:

Fifty-three patients (87% men, mean age 58.7±9.0 years) with suspected coronary artery disease were included prospectively. All patients underwent serial [ 15 O]H 2 O positron emission tomography perfusion imaging at baseline and after revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. FFR was routinely measured at baseline and directly post-PCI. After revascularization, regional rest and stress MBF improved from 0.77±0.16 to 0.86±0.25 mL/min/g and from 1.57±0.59 to 2.48±0.91 mL/min/g, respectively, yielding an increase in coronary flow reserve from 2.02±0.69 to 2.94±0.94 ( P <0.01 for all). Mean FFR at baseline improved post-PCI from 0.61±0.17 to 0.89±0.08 ( P <0.01). After PCI, an increase in FFR paralleled improvement in absolute myocardial perfusion as reflected by stress MBF and coronary flow reserve ( r = 0.74 and r = 0.71, respectively, P <0.01 for both). PCI demonstrated a greater improvement of regional stress MBF as compared with coronary artery bypass graft surgery (1.14±1.11 versus 0.66±0.69 mL/min/g, respectively, P =0.02). However, patients undergoing bypass grafting had a more advanced stage of coronary artery disease and more incomplete revascularizations.

Conclusion:

Successful coronary revascularization has a significant and positive impact on absolute myocardial perfusion as assessed by serial quantitative [ 15 O]H 2 O positron emission tomography. Notably, improvement of FFR after PCI was directly related to the increase in hyperemic MBF.

Coronary flow velocity reserve by echocardiography: feasibility, reproducibility and agreement with PET in overweight and obese patients with stable and revascularized coronary artery disease

Background

Coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography of the LAD is used to assess microvascular function but validation studies in clinical settings are lacking. We aimed to assess feasibility, reproducibility and agreement with myocardial flow reserve (MFR) measured by PET in overweight and obese patients.

Methods

Participants with revascularized coronary artery disease were examined by CFVR. Subgroups were examined by repeated CFVR (reproducibility) or Rubidium-82-PET (agreement). To account for time variation, results were computed for scans performed within a week (1-week) and for all scans regardless of time gap (total) and to account for scar tissue for patients with and without previous myocardial infarction (MI).

Results

Eighty-six patients with median BMI 30.9 (IQR 29.4–32.9) kg × m⁻² and CFVR 2.29 (1.90–2.63) were included. CFVR was feasible in 83 (97 %) using a contrast agent in 14 %. For reproducibility overall (n = 21) limits of agreement (LOA) were (−0.75;0.71), within-subjects coefficient of variation (CV) 11 %, and reliability 0.84. For reproducibility within 1-week (n = 13) LOA were (−0.33;0.25), within-subjects CV 5 %, and reliability 0.97. Agreement with MFR of the LAD territory (n = 35) was without significant bias and overall LOA were (−1.40;1.46). Agreement was best for examinations performed within 1-week of participants without MI of the LAD-territory (n = 12); LOA = (−0.68;0.88).

Conclusions

CFVR was highly feasible with a good reproducibility on par with other contemporary measures applied in cardiology. Agreement with MFR was acceptable, though discrepancy related to prior MI has to be considered. CFVR of LAD is a valid tool in overweight and obese patients.

Coronary microvascular dysfunction: an update

Many patients undergoing coronary angiography because of chest pain syndromes, believed to be indicative of obstructive atherosclerosis of the epicardial coronary arteries, are found to have normal angiograms. In the past two decades, a number of studies have reported that abnormalities in the function and structure of the coronary microcirculation may occur in patients without obstructive atherosclerosis, but with risk factors or with myocardial diseases as well as in patients with obstructive atherosclerosis; furthermore, coronary microvascular dysfunction (CMD) can be iatrogenic. In some instances, CMD represents an epiphenomenon, whereas in others it is an important marker of risk or may even contribute to the pathogenesis of cardiovascular and myocardial diseases, thus becoming a therapeutic target. This review article provides an update on the clinical relevance of CMD in different clinical settings and also the implications for therapy.

Off-pump coronary artery bypass grafting using a bilateral internal mammary artery Y graft

Objective

To evaluate the outcome of off-pump coronary artery bypass grafting (OPCABG) using a bilateral internal mammary artery (BIMA) Y configuration graft to achieve total arterial myocardial revascularization.

Methods

From October 2002 to December 2008, 208 patients (196 males and 12 females) underwent OPCABG using a BIMA Y configuration graft. The average age of the patients was 56.5 ± 11.3 years, with an age range of 33–78 years. A total of 167 (80.2%) cases had triple-vessel disease. Left main stem disease was found in 33 (15.9%) cases, and double-vessel disease was found in 8 (3.9%) cases. The semi-skeletonization technique was used to harvest the two internal mammary arteries (IMAs), and then the free right internal mammary artery was connected end-to-side to the left internal mammary artery (LIMA) in situ to complete the Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery in all patients. Graft patency was assessed intra-operatively with the HT311 transit time flowmeter.

Results

A total of 728 distal anastomoses were performed in 208 patients, with the average being 3.5 ± 1.3 per person. No one died or experienced recurrent angina within 30 days after the operation.

Conclusions

OPCABG using the BIMA Y graft was safe and effective to achieve total arterial revascularization. This method avoids surgical operation on the ascending aorta and other incisions.

Total Arterial Off-pump Coronary Revascularization with a Bilateral Internal Mammary Artery Y Graft (208 cases)

Objective:

The aim was to evaluate the early outcome of off-pump coronary artery bypass grafting (OPCABG) with a bilateral internal mammary artery (BIMA) Y configuration graft to achieve total arterial myocardial revascularization.

Materials and Methods:

From October 2002 to December 2008, 208 patients (196 male and 12 female patients) underwent OPCABG by only using a BIMA Y configuration graft. The average age of the patients was 56.5±11.3 years, with the age range being 33–78 years. A total of 167 (80.2%) cases had triple-vessel disease. Left main stem disease was found in 33 (15.9%) cases, and double-vessel disease was found in 8 (3.9%) cases. The semiskeletonization skill was used to harvest the two IMAs, and then the free right internal mammary artery was anastomosed end-to-side to the in situ left internal mammary artery to composite a Y configuration graft. Off-pump and sequential anastomosis methods were used to perform coronary artery bypass surgery for the patients. Graft patency was assessed by using the HT311 transit time flowmeter (USA Transonic Systems Inc.), intraoperatively.

Results:

We performed distal anastomoses of the grafts in 728 patients, the average being 3.5±1.3 per person. No one died and got recurrent angina within 30 days after operation.

Conclusion:

OPCABG by using the BIMA Y graft was safe and effective to achieve total arterial revascularization, and avoid surgical operation on the ascending aorta, and other incisions.

Regional myocardial blood flow measured by stress multidetector computed tomography as a predictor of recovery of left ventricular function after coronary artery bypass grafting

BACKGROUND

Multidetector-row computed tomography (MDCT) applications have expanded to evaluation of myocardial blood flow (MBF) and viability. We quantified regional MBF pre- and post-coronary artery bypass grafting (CABG) using adenosine stress and cardiac 64-MDCT, and investigated whether the results predict MBF and left ventricular (LV) function recovery after CABG.

METHODS

We studied 321 regions in 19 CABG patients who underwent adenosine stress 64-row MDCT perfusion imaging and cine magnetic resonance imaging pre- and post-CABG. Myocardial blood flow was estimated from linear regression equation slopes using Patlak plot analyses and compared with LV function by measuring wall thickening (%WT) using cine magnetic resonance imaging.

RESULTS

Overall mean MBFs were 1.39 +/- 0.49 and 1.95 +/- 0.49 mL/(g min) pre- and post-CABG (P < .0001). Myocardial blood flow in revascularized areas increased significantly (pre-CABG 1.18 +/- 0.45, post-CABG 1.99 +/- 0.66 mL/[g min], P < .001), whereas nonischemic areas showed no difference (1.79 +/- 0.70 and 1.97 +/- 0.46 mL/[g min], P = .14). Revascularized areas with preoperative MBF > or = 0.9 mL/(g min) showed significantly greater MBF improvement than those with preoperative MBF <0.9 mL/(g min) (P = .04). In patients with preoperative LV dysfunction (ejection fraction <40%), %WT in revascularized areas with pre-CABG MBF > or = 0.9 mL/(g min) improved significantly after CABG (pre-%WT 40.9 +/- 22.9, post-%WT 52.8 +/- 20.6, P = .03) versus those with pre-CABG MBF <0.9 mL/(g min) (pre-%WT 53.2 +/- 35.5, post-%WT 42.5 +/- 17.0, P = .40).

CONCLUSIONS

Our results demonstrated more significantly increased MBF post-CABG than pre-CABG, particularly in revascularized areas. Regional MBF before CABG may predict MBF and LV function recovery, in the short term, after CABG.

Advances in coronary microvascular dysfunction

Considerable focus has been directed towards coronary arterial disease in the management of coronary heart disease, however the coronary microcirculation plays a major role in the regulation of coronary blood flow. Thus while we have multiple medical and revascularisation therapies to treat large vessel coronary artery disease, therapies directed towards the microcirculation are very limited. This review paper summarises important aspects of coronary microvascular dysfunction including (a) methods of assessment, (b) clinical classification of associated disorders, (c) possible pathophysiological mechanisms, and (d) potential therapies. Hence this will provide important background to advancing our understanding and management of coronary heart disease by targeting the coronary microcirculation.

Analog electrical model of the coronary circulation in case of multiple revascularizations

In this work, we propose an analog electrical model of the coronary circulation for patients with obstructive disease undergoing revascularization. In this clinical situation, the collateral circulation to the occluded artery is difficult to ascertain via preoperative measurements and well-developed collaterals might induce long-term restenosis of the revascularized artery due to flow competition mechanisms. The proposed model allows an original biomechanical analysis of per-operative hemodynamic data in order to assess quantitative evaluation of pressures and flows inside the native stenosed arteries, the collateral network and the bypass grafts. Average cardiac cycle values are analysed. In the case of 3-vessel disease and chronic occlusion of the right coronary artery, the quantitative results confirm the protective effects of the collateral flows in the pathological situation, but also show that the revascularization of the occluded right artery is fully justified since the collateral flows remain low, even when the left territory is revascularized. The model thus provides a computational tool to evaluate therapeutic strategies for each patient.

Progressive improvement of myocardial perfusion after off-pump revascularization with bilateral internal thoracic arteries: Comparison of early versus 1-year postoperative myocardial single photon emission computed tomography

OBJECTIVE

We evaluated the time course of myocardial perfusion improvement after off-pump revascularization.

METHODS

Seventy-six patients who underwent off-pump coronary bypass with bilateral internal thoracic arteries for revascularization of the left coronary territory were studied. Myocardial single photon emission computed tomography was performed preoperatively and at 3 months and 1 year postoperatively. Myocardial perfusion was quantified with automatic software, and the left coronary territory was divided into 16 segments. As an indicator of the ischemic myocardium, the reversibility score was defined as a measure of rest minus stress perfusion values. A total of 403 segments that showed a reversibility score of 7 or greater preoperatively were included.

RESULTS

The reversibility score was improved significantly at 3 months postoperatively (P < .001) and further improved 1 year after the operation (P < .001). When the patients were divided into 2 groups based on the type of bilateral internal thoracic arteries used (group Y: Y-composite graft, n = 39; group I: bilateral in situ grafts, n = 37), the reversibility score was improved significantly 3 months after the operation (P < .001) and further improved 1 year after the operation (P < .001) in both groups. There were no significant differences in the reversibility scores between groups Y and I at postoperative month 3 (P = .463). The scores approached zero in both groups at 1 year postoperatively (group Y, -1.7% +/- 7.9%; group I, 1.3% +/- 7.2%).

CONCLUSIONS

The myocardial reversibility score improved greatly during the first 3 months after the operation and further improved until 1 year postoperatively. Perfusion improvement was similar between the Y-composite and bilateral in situ internal thoracic artery grafts in terms of the reversibility score.

Controversies in the Use of Intraluminal Shunts During Off-Pump Coronary Artery Bypass Grafting Surgery

Technical advances have made the performance of multivessel off-pump coronary artery bypass feasible. Snaring and intraluminal shunts are the techniques used for vascular control. Snaring provides a bloodless surgical field, is usually well tolerated by the patient, and is supported by years of clinical experience. Intraluminal shunts aim to achieve hemostasis at the arteriotomy site and to allow antegrade flow to provide myocardial protection. There are unresolved issues regarding whether shunts have a clinical benefit, do provide adequate flow to provide myocardial protection, and whether they cause significant endothelial damage. In this article, we have reviewed the literature to lend perspective to these issues.

Total Arterial Revascularization with a Single Y-Composite Graft for Triple-Vessel Disease: Comparison of 2- and 3-Artery Grafts

BACKGROUND

Treating triple-vessel disease by grafting a single Y-composite graft with 1 arterial conduit attached to the side of the internal thoracic artery is sometimes not used because of the possibility of hypoperfusion.

METHODS

Between March 2001 and June 2003, 271 patients who underwent total arterial revascularization for triple-vessel disease were divided into 2 groups. Group I (n = 188) received a Y-composite graft with 2 arterial conduits, and group II (n = 83) received a Y-composite graft and 1 additional arterial conduit. We retrospectively reviewed the data and compared the clinical results of the 2 groups.

RESULTS

The numbers of distal anastomoses were 3.9 +/- 0.7 (mean +/- SD) per patient in group I and 4.1 +/- 0.8 in group II (P = .021). There were 2 in-hospital deaths in group I and none in group II (difference not statistically significant). Perioperative myocardial infarction occurred in 2 patients in group I and none in group II (not statistically significant). No patient in either group needed a new intra-aortic balloon pump postoperatively, and no patients experienced hypoperfusion syndrome. A cerebrovascular accident occurred in 1 patient of each group. During the follow-up period (15.9 +/- 6.7 months in group I, 25.2 +/- 8.3 months in group II), 5 patients died (4 in group I, 1 in group II). Two patients in group I and 1 patient in group II needed an intervention on the right coronary artery, but the other patients required no additional procedures and had no symptoms of angina. There were no statistically significant differences in survival and reintervention-free survival between the 2 groups.

CONCLUSION

Single Y-composite grafts with 2 arterial conduits may be a safe and effective strategy for treating triple-vessel disease.

Myocardial viability, coronary flow reserve, and in-hospital predictors of late recovery of contractility following successful primary stenting for acute myocardial infarction

OBJECTIVE

To assess the relation between myocardial viability, coronary flow reserve, and recovery of myocardial contractility after stenting for acute myocardial infarction.

DESIGN

Consecutive sample prospective study.

SETTING

University hospital.

PATIENTS

41 patients with single vessel disease and successful primary stenting for a first acute myocardial infarction.

INTERVENTIONS

(201)Tl single photon emission computed tomography, contrast ventriculography, and intracoronary Doppler performed 7 (1) days after primary stenting.

MAIN OUTCOME MEASURES

Regional contractility recovery assessed by contrast ventriculography at 6 (1) months' follow up.

RESULTS

On univariate analysis, contractility recovery was correlated to prereperfusion anterograde and collateral flow grades (r = 0.41, p = 0.03 and r = 0.55, p = 0.0004), viability index (r = 0.55, p = 0.04), peak creatine kinase concentrations (r = -0.55, p = 0.0005), left ventricular ejection fraction (r = 0.45, p = 0.005), end diastolic pressure (r = -0.62, p < 0.0001), end systolic volume index (r = -0.47, p = 0.01), and the extent of hypokinetic area (r = -0.48, p = 0.003), but not the coronary flow reserve. On multivariate analysis, independent predictors of late contractility recovery were prereperfusion anterograde and collateral flow grades and viability index. Relative coronary flow reserve, reflecting the culprit vessel's microvascular function, was correlated only to the extent of the infarct risk area (r = -0.45, p = 0.003).

CONCLUSIONS

Independent predictors of contractility recovery between the seventh day and the sixth month after successful stenting for acute myocardial infarction are prereperfusion anterograde and collateral flows and myocardial viability. The culprit vessel's microvascular dysfunction is independent of myocardial viability and contractility and correlated to the extent of "jeopardised microvasculature".

Composite arterial Y graft has less coronary flow reserve than independent grafts

BACKGROUND

It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocardial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts.

METHODS

Positron emission tomography was performed at rest and after dipyridamole infusion using oxygen-15-labeled water 2 weeks after coronary artery bypass grafting. Regional MBF was calculated in seven segments of the left ventricle. Coronary flow reserve was defined as the ratio of MBF after dipyridamole infusion to MBF at rest. In the Y graft group (n = 22), a free arterial graft to obtuse marginal arteries was anastomosed to the proximal side of in situ left internal thoracic artery, which was anastomosed to the left anterior descending artery. In the independent graft group (n = 13), left anterior descending and obtuse marginal arteries were independently revascularized using in situ left internal thoracic artery and a free arterial graft.

RESULTS

There was no difference between the groups in MBF at rest. Coronary flow reserve in the Y graft group was lower than that in the independent group in the anterobasal (1.43 +/- 0.07 versus 1.90 +/- 0.13, p = 0.038), apical (1.24 +/- 0.06 versus 1.64 +/- 0.12, p = 0.003), septal (1.34 +/- 0.05 versus 1.75 +/- 0.13, p = 0.023), and lateral regions (1.19 +/- 0.04 versus 1.66 +/- 0.09, p = 0.001).

CONCLUSIONS

Although arterial composite Y graft improved MBF at rest, it was not as effective as independent grafts for improving coronary flow reserve soon after coronary artery bypass grafting.

The contribution of positron emission tomography to the study of ischemic heart failure

Cardiac imaging with positron emission tomography offers unrivaled sensitivity and specificity to probe cardiovascular physiology in health and disease. The use of positron emission tomography to noninvasively measure regional myocardial blood flow and assess myocardial viability in patients with ventricular dysfunction and coronary artery disease has contributed greatly to our understanding of the pathophysiology of ischemic heart failure. The advances and the need for further studies to establish both the natural history of such ventricular dysfunction and the role of coronary revascularization are discussed.